Cathode-ray tube and the like



CATHODE RAY TUBE AND THE LIKE Original Filed Sept. 4, 1936 H TiTl.

Zhwentor Patented Feb. 6, I940 UNITED STATES PATENT OFFICE 2,189,281CATHODE-RAY TUBE AND THE LIKE Original application stpkmbel' 4. 1936.Serial No.

6 Claims.

This invention relates to cathode-ray tubes and more particularly tocathode ray tubes of the composite metal-glass type.

An object of the invention is to provide an improved cathode-ray tube ofthe typehaving a composite metal-glass flare portion.

In cathode-ray tubes of the type wherein the end of the neck pOrtionQitis requisite that this flared portion be of comparatively largediameter, especially in the larger tubes where even the reduced end ofthe metal part of the envelope may be of the order of several inches indiameter. While the reduced end of the metal part of the envelopecambyordinary methods, be made to very accurate dimensions, the same is nottrue of the manufacture of the co-operating flared end of the glass neckportion. While methods of flaring a glass tube to a relatively largediameter are well-known, I have foundthat these methods are not suitablefor use in forming the flared portion of the tube neck. Furthermorethese usual methods of flaring aglass tube to large diameters, are slowand highly accurate dimensions cannot be produced with sufficientuniformity and reliability to warrant their use in quantity productionof large cathode-ray tubes.

Accordingly it is aprincipal feature of the present invention to providea composite metalglass cathode-ray tube envelope, which is suited toquantity production, and wherein the flared neck portion of the tube canbe made with a very high degree of accuracy and uniformity.

Another feature relates to the novel organization, arrangement andrelative location of partsv which constitute an improved compositemetalglass cathode-ray tube envelope.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

In the drawing, Fig. 1 is a schematic sectional view of a device toexplain the method of form ing certain parts of a cathode-ray tubeenvelope according to the invention.

Fig. 2 is a sectional view to illustrate another step in the formationof the cathode-ray tube envelope.

Divided and this application June 29, 1937, Serial No. 150,906

Fig. 3 is a view of the completed cathode-ray tube made in accordancewith the invention.

Referring more particularly to Fig. 3, the oathode-ray tube envelope isof the composite metalglass type and comprises a substantially flat endwall I of glass or similar vitreous material having its interior facecoated with suitable fluorescent material (not shown). The envelopecomprises an elongated conical portion 2 of steel or other suitablemetal. The neck portion of the envelope comprises 'a substantiallycylindrical glass tubular portion 3 terminating at its left-hand end inan enlarged flare I. Inasmuch as it is not practical to form avacuum-tight seal between the,

metal 2 and the glass 3, there is interposed a frusto-conical ring 5 ofa metal which has the same coeflicient of expansion as the glass 4.Preferably the flare l is of Coming 705 AJ glass, and the ring 5 is of"Kovar an alloy consisting of approximately 18% cobalt, 28% nickel and54% iron. After the parts I to i-have been assembled as describedhereinbelow, the envelope has mounted therein the usual electrodeassembly, and the tube is then exhausted and processed according toknown procedure. After the tube has been processed and sealed-off, itmay have fastened thereto a contact base 6 with appropriate contactprongs 1.

As, will be seen from the foregoing description, the metal portions 2and 5 are of rigid metal and in orderto-effect a proper vacuum-tightseal between members 4 and 5 it is necessary that the mouth of the flare,be of accurate diameter. I have found that the ordinary methods offlaring a glass tube and uniting it to a metal ring are not suitable foruse in cathode-ray tubes of'the type described, either because of thetime re-.

quired to effect the proper seal, or because of the lack of reliabilityor uniformity in the seal.

- Iv have also found that by employing a special pressure moldingoperation it is possible to overcome the above-noted disadvantages, andas a result relatively large composite metal-glass cathode-ray tubeenvelopes can be made comparatively economically and with accuratedimensions.

Referring toFig. 1 a description will now be given of the manner ofsimultaneously-forming the flare 4 and sealing it in a vacuum-tightmanner'to ring 5. In Fig. 1 the numeral 8 represents schematically asuitable mold having a frustoconical mold cavity terminating at itsbottom in a reduced cylindrical cavity. The mouth of the conical cavityis provided with a raised rim 9 for the purposes about to be described.The metal ring 5 is seated on the rim of the mold as shown,

so that the lower edge of the frusto-conical portion l0- extendsinto themold cavity beyond the rim 9 thus providing a slight clearance betweenthe said edge and the face of the mold cavity.

The clamping ring II is placed in position to hold the ring 5 rigidly inplace. A gather or ball'of molten glass preferably at white heat is thenallowed to fall into the mold cavity and immediately thereafter theplunger I2 is lowered to force the liquid glass upward until it engagesthe edge of ring 5 and flows therearound as shown. It will be noted thatthe head of the plunger I2 is shaped complementary to the mold cavity sothat when said plunger is in its lowermost posisaid edge has beenpreviously oxidized in any wellknown manner. There is thus formedcomposite metal-glass assembly consisting of an accurately dimensionedfrusto-conical glass part sealed in a vacuum-tight manner to the Kovarring 5.

After the composite metal-glass assembly has cooled sufliciently in the.mold, whereupon it may be removed and annealed in any well knownmanner. The annealed assembly is mounted in a suitable air-tight jigsuch for example as shown in Fig. 2 comprising a rotatable head l4 and aclamping ring l5, adapted to be held in place by suitable springs IS.The hub I1 is provided with a passage-way l8 leading to a blowing hosefor purposes to be described. With the assembly as I shown in Fig. 2 setin rotation, the glass blower then heats the end to .softenit, and atthe proper instant he blows through passage I8 to blow the end 20 to abubble which can then be broken on. By means of a carbon rod or paddlethe edge I9 is straightened and smoothed to the proper diameter, whilethe said part I9 is still within the softening flame. A suitable lengthof glass tubing 3 is then placed in axial alignment with the end l9 andthe two are sealed together in the manner well-known in the glassblowing 811).

-When the joining of the cylindrical glass neck portion 3 has beencompleted, theclamp I5 is removed and the assembly comprising elements3,1 and 5 is united to the metal member 2. Preferably the rim of ring 5is welded to the reduced end of member 2 to form a vacuum-tight sealtherewith. The finished composite metalglass envelope is then ready toreceive the electrode assembly or mount.

It will be understood of course that the glass end I may be sealed tothe metal member 2 either before or after the union of parts 2 and 5 asabove-described. Likewise the parts 2 and 5 may be welded-togetherv as aunit prior to sealing thereto the glass flare as above-described. Inthis latter case the mold will be provided with a suitable clampingmember to hold the parts rigidly in place during the pressure on theglass "gather" in the mold as described.

Other modifications may be made inthe method described, withoutdeparting fromthe spirit and scope of the invention. For a detaileddisclosure of preferred forms of electron guns, control electrodes, anddeflecting means that may be used with the tube as described, referencemay be had to application Serial No. 95,970, filed August 14, 1936.

This application is a division of application Serial No. 99,384, filedSeptember 4, 1936.

What I claim is:

1. A cathode-ray tube having a main funnelshaped body portion of metal,an elongated cylindrical glass neck joined to a composite glassmetalflare said flare comprising a frusto-conical glass section and a metalsealing ring with a corresponding frusto-conical section, said sealingring being of a metal different from that of said body portion andsealed to the glass section in a vacuum-tight manner, the parts of saidcomposite flare being preformed and sealed together as a separate unitfrom the remainder of the tube, a vacuum-tight weld between said ringand the constricted end of said body portion, a glass window sealed in avacuum-tight manner to-the enlarged end of said body portion, and raydeflecting means adjacent the glass section of said composite flare.

2. A cathode-ray tube according to claim 1 in which the glass section ofthe composite flare and the metal sectionthereof have substantially thesame angular opening.

3. A cathode-ray tube according to claim 1 in which the said sealingring has a frusto-conical flare portion where it is sealed to thecorresponding frusto-conical glass section of the composite flare.

4. A cathode-ray tube according to claim 1 in which said main metal bodyportion has a cylindrical dollar at its narrow end and said sealing ringhas a cylindrical portion welded to said collar and a frusto-conicalportion sealed into the corresponding frusto-conical glass section ofthe composite flare.

5. A composite metal-glass flare unit for joining an elongated glassneck to the metal body section of a cathode-ray tube which glass neckhas a difierent coeilicient of expansion from that of said metal bodysection comprising a metal ring having a preformed frusto-conicalsection sealed in a vacuum-tight manner to a preformed correspondingfrusto-conical glass section, said ring and glass section being formedas a separate unit and having substantially the same expansioncoeflicient.

6. A cathode-ray tube having a main body portion of metal, an elongatedcylindrical glass neck joined to a composite glass-metal flare saidflare comprising a frusto-conical glass section and a metal sealing ringwith a corresponding frustoconical section, said sealing ring being of ametal different from that of said body portion but having the sameexpansion coeflicient as said glass section, whereby it is sealed to theglass section in a vacuum-tight manner, the parts of said compositeflare being preformed and sealed together as a separate unit from saidcylindrical glass neck and the remainder of the tube, a vacuum-tightweld between said ring and the constricted end of said body portion, aclosure member sealed in a vacuum-tight'manner to the enlarged end ofsaid body portion, and ray deflecting means adjacent the glass sectionof said composite flare. I

ROBERT M. BOWIE.

